Surveying pole with compensated tilt measurement and method implemented in a surveying pole

Abstract

A surveying pole comprising: a rod extending between a first end and a second end, wherein a top unit including a tilt sensor is mounted at one end and a pointing tip is located at the opposite end. A light emitting unit is configured to send a collimated light beam for propagation from one of said first and second ends to the other end. A detector arrangement is configured to detect a position of said collimated light beam at said other end. A processor is configured to compare the detected position with a reference position and determine a deviation error representative of a bending of said rod, wherein the processor is further configured to obtain a position of the pointing tip using the determined deviation error, wherein said reference position corresponds to a position of the collimated light beam at the other end for a known bending of said rod.

1 . A surveying pole comprising:
 a rod extending between a first end and a second end, wherein a top unit including a tilt sensor is mounted at one of said first and second ends, and a pointing tip is located at the opposite end relative to the top unit,   a light emitting unit configured to send a collimated light beam for propagation from one of said first and second ends to the other end,   a detector arrangement configured to detect a position of said collimated light beam at said other end; and   a processor configured to compare the detected position with a reference position and determine a deviation error representative of a bending of said rod based on said comparison, wherein the processor is further configured to obtain a position of the pointing tip of the surveying pole using the determined deviation error, wherein said reference position corresponds to a position of the collimated light beam at the other end for a known bending of said rod.   
     
     
         2 . The surveying pole of  claim 1 , wherein the detector arrangement includes an imaging device arranged within said rod at said other end, wherein said imaging device is configured to detect the position of said collimated light beam as a position on a pixel array of said imaging device at which said collimated light beam impinges and creates a light spot. 
     
     
         3 . The surveying pole of  claim 1 , wherein the detector arrangement includes an imaging device arranged in proximity of said other end for imaging a light spot created by said collimated light beam on a surface located at said other end, or at a predetermined distance from said other end, wherein said imaging device is configured to detect the position of said collimated light beam as a position of the image of said light spot on a pixel array of said imaging device. 
     
     
         4 . The surveying pole of  claim 3 , wherein the imaging device is arranged at a fixed position relative to said other end and wherein the detector arrangement further includes a lens arrangement for focusing said imaging device on said surface. 
     
     
         5 . The surveying pole of  claim 2 , wherein the light emitting unit and the imaging device are located at opposite ends of said rod. 
     
     
         6 . The surveying pole of  claim 1 , wherein the detector arrangement includes a pattern internally arranged in said rod at a surface located at said other end, or at a predetermined distance from said other end, and an imaging device arranged to capture at least one image of said pattern with said collimated light beam hitting said pattern, wherein the position of said collimated light beam is detected as a position at which the collimated light beam hits said pattern. 
     
     
         7 . The surveying pole of  claim 6 , further including a lens arrangement for focusing said imaging device at said surface. 
     
     
         8 . The surveying pole of  claim 6 , wherein said pattern and said light emitting unit are located at opposite ends of said rod. 
     
     
         9 . The surveying pole of  claim 6 , wherein said surface and the imaging device are located at opposite ends of said rod. 
     
     
         10 . The surveying pole of  claim 1 , wherein the detector arrangement includes an imaging device and a reflecting element, wherein the reflecting element is arranged at said other end, or at a predetermined distance from said other end, for reflection of said collimated light beam towards said imaging device arranged to detect the position of the collimated light beam as a position on a pixel array of said imaging device at which the light beam reflected at said reflecting element impinges. 
     
     
         11 . The surveying pole of  claim 10 , wherein the reflecting element is one of a mirror or a retroreflector. 
     
     
         12 . The surveying pole of  claim 1 , wherein said collimated light beam propagating from one of said first and second ends to said other end includes a light pattern, wherein the detector arrangement includes an imaging device arranged at said other end and an optical element for imaging said light pattern on a pixel array of said imaging device, wherein the imaging device is configured to detect the position of the collimated light beam as a position of an image of the light pattern on said pixel array. 
     
     
         13 . The surveying pole of  claim 12 , wherein the light emitting unit includes a light source configured to emit light, an optical element providing a light pattern in the light emitted from the light source and an optical element configured to provide said collimated light beam including said light pattern for propagation from one of said first and second ends to said other end. 
     
     
         14 . The surveying pole of  claim 6 , wherein the light emitting unit is arranged in said top unit, at said first end or at said second end. 
     
     
         15 . The surveying pole of  claim 6 , wherein the light emitting unit is a laser, such as a light emitting transmitter of an electronic measurement device (EDM) arranged within the top unit. 
     
     
         16 . The surveying pole of  claim 6 , wherein the light emitting unit is arranged to emit light along a longitudinal axis of said rod when it is unbent. 
     
     
         17 . The surveying pole of  claim 16 , further comprising a beam splitter arranged along said longitudinal axis so that an imaging device of said detector arrangement is arranged to detect said collimated light beam from a direction intersecting said longitudinal axis. 
     
     
         18 . The surveying pole of  claim 6 , wherein the reference position corresponds to a position at which the light beam hits the target for said rod being unbent. 
     
     
         19 . The surveying pole of  claim 6 , wherein the rod is a telescopic pole arrangement. 
     
     
         20 . A method implemented in a surveying pole comprising a rod extending between a first end and a second end, wherein a top unit including a tilt sensor is mounted at one of said first and second ends, and a pointing tip is located at the opposite end relative to the top unit, said method comprising:
 sending a collimated light beam for propagation from one of said first and second ends to the other end;   detecting a position of said collimated light beam at said other end;   comparing the detected position with a reference position;   determining a deviation error representative of a bending of said rod based on said comparison; and   obtaining a position of the pointing tip of the surveying pole using the determined deviation error, wherein said reference position corresponds to a position of the collimated light beam at the other end for a known bending of said rod.